Abstract Atrial fibrillation (AF) is the most common arrhythmia and affects over 2 million Americans, a number that is expected to rise to between 6 and 12 million by 2050. AF is a major public health burden as it is associated with a five-fold increased stroke risk, doubling in dementia risk, tripling in heart failure risk, and nearly two-fold increase in mortality. Many risk factors for AF have been identified, including advancing age, male sex, hypertension, heart failure, obesity and family history. Despite the profound socioeconomic costs of AF, our understanding of the fundamental mechanisms for the arrhythmia remains limited. The central goal of the candidate's research is to identify novel genes and pathways for AF. The candidate is a cardiac electrophysiologist with a bench to bedside research focus on AF. He has developed a cohort of patients with lone AF, leads an international consortium of investigators studying the genetics of AF, and performs laboratory work on the mechanisms of AF. Despite the success that the candidate has had in developing an arrhythmia research program, his current clinical commitments are limiting his exposure to the increasing number of fellows that he is mentoring. Therefore, the specific aims of this application are to provide the candidate long-term support to enable a reduction in his clinical commitments, and thus expand the training of mentees interested in pursuing patient-oriented arrhythmia research. Research mentees will have a rich diversity of opportunities to participate in patient-oriented research through the MGH AF study, the CHARGE-AF Consortium, and the candidate's own translational laboratory work. The fellow's research activities will be complemented by the extensive educational resources available at Massachusetts General Hospital and Harvard University. Ultimately, if funded, this application will contribute to the development of new clinical investigators in arrhythmia research and will catalyze understanding of this common and morbid arrhythmia.